Large daphnia (lat. Daphnia magna) is a permanent inhabitant of any fresh water body.

It is sometimes called the freshwater or water flea and is familiar to many aquarium hobbyists as it is an excellent food for aquarium fish. It belongs to the family Daphniidae (Daphniidae) from the order Leaf-legged crustaceans (Onychura).

Habitat

The ideal place for the settlement of daphnia are village ponds, in which there is a lot of manure and oxygen-depleted water. Water fleas are resistant to changes in the amount of oxygen in the water. This is due to the fact that they are able to independently synthesize hemoglobin.

With a decrease in oxygen, hemoglobin in daphnia increases. They turn bright red and increase in number. With a normal oxygen content, the crustaceans have a yellow-pink color.

Small crustaceans are permanent inhabitants of fresh water bodies, deep lakes, and small puddles. Many of them move along the bottom of the reservoir or the leaves of aquatic plants, and some scurry along the surface, periodically waving their antennae.

good place habitats for the water flea are small puddles and roadside ditches. In them, the water temperature is close to atmospheric and enriched with oxygen. The drying up of shallow reservoirs threatens the death of all its inhabitants.

reproduction

The reproduction of Daphnia is accompanied by a process of heterogony. In the case of favorable conditions in the form of rainfall and filling all the hollows with fresh water, only females emerge from the fertilized eggs. After a week, they reach puberty and proceed to procreation.

Up to a hundred eggs are laid in the female's brood chamber. The higher the temperature environment the faster they develop. Young daphnia are born into the world in a brood chamber. After that, the mother molts and lays the next batch of eggs. After one week, a new generation of juveniles is ready to breed.

Two months later, the water in the puddle is already teeming with water fleas. Such overpopulation often leads to death a large number daphnia. Then the surviving females begin to lay eggs, from which individuals of different sexes emerge.

After mating, the female lays 2 eggs. Cells appear under their shell, which surround the eggs in a dense layer, and a chitinous shell is created on top of these cells, which leads to the appearance of ephippium in the brood chamber.

Eggs placed in such a capsule are provided with a huge supply of nutrients and look bigger than usual. They can stay for a long time in a dried-up reservoir or frozen in ice, while maintaining their viability.

Sticking to the paws of birds, clinging to the fur of animals, to frogs or aquatic insects, they are easily transferred from one reservoir to another. Under favorable conditions, a new generation of females emerge from them, which give birth to a new population of water fleas.

Daphnia are excellent food for freshwater fish and other creatures living near water. They reproduce at an astonishing rate. If all her offspring survived, then in just one season it would reach 30 million individuals.

Behavior

Daphnia large in large quantities inhabit reservoirs, briskly scurrying through the water column. They move in short nets, simultaneously waving their antennae. For the spasmodic way of moving in the water, they received the name of water fleas.

Daphnia are active all day long. At night, they swim closer to the surface of the water, and during the day they sink to the very bottom. They have from 4 to 6 pairs of pectoral legs equipped with bristles. Such a filtering apparatus is used to obtain food.

The main food of water fleas is protozoa, algae, detritus particles and bacteria. Daphnia do not use sight while hunting. Their eyes can only distinguish between light and shadow. During the movement of the legs, food enters the filter chamber along with the flow of water.

Morphology

The pectoral lobes of the pectoral legs are turned into gills. Small claws are designed to clean the shell, and the back of the body is bent towards the abdomen. The transparent body of daphnia allows you to see under a microscope its internal organs - the esophagus, circulatory system, blood circulation and brood chamber.

The size of the female is about 6 mm, and the male is up to 2 mm. The round head does not have a neck interception. One compound eye was obtained by merging two lateral ones. The first pair of antennas is small. The rear antennae are more developed and are used as oars. The body is strongly flattened laterally. The double-leaved oval shell hides the entire body, leaving the head free.

The brood chamber is located on the back. The shell ends tail spike.The life expectancy of large daphnia does not exceed 19 days.

.

For many aquarium fish lovers, daphnia is used as food for pets living in it. Its content cannot be called simple, since timely care is required with proper nutrition. Now you can buy food in specialized stores. However, earlier it was bought on the market or cooked on its own, caught in natural reservoirs of planktonic crustaceans.

This object has 2 eyes

Appearance and structure

Many people associate Daphnia with dry fish food. In fact, these are small crustaceans living in all stagnant continental water bodies. They belong to the genus of planktonic crustaceans. Another common name is water flea.

The cladocerans, called daphnia, usually have two eyes per head. However, sexually mature individuals can sometimes be distinguished by one double eye and an additional eye located close to it. It is the unpaired organ that is responsible for vision. In the area of ​​​​the small head, there are also two pairs of small antennae. The distant pair is larger and covered with bristles. With their light movement, the crustaceans make a peculiar movement in the form of a jump. Due to this feature, they began to be called water fleas.

In this video you will learn more about Daphnia:

The size of the body of daphnia varies, since it depends on its species and ranges from 2 to 6 mm. Such a tiny size of the body does not allow a good view of its structure. What it looks like can only be seen under a microscope.

The body of the crustacean has an oval shape and is covered with a special frame on both sides. It serves as protection for internal organs. The anterior antennae on the head are the organ of smell. Due to the antennae, daphnia moves along the water surface:

• repelled;
• floats;
• makes jumps.

There are many types of these crustaceans

The crustacean has pectoral legs, which have the ability to pass single-celled bacteria and algae through themselves. In this area there are gill sacs with which the water flea breathes. They are covered with many bristles that serve as a kind of filter. In 1 minute, the legs make up to half a thousand strokes.

The genus of these cladocerans includes more than 150 species. Common in our area:

• magna - the largest;
• puleks - medium size;
• mine is small.

The stomach of any daphnia is always full of plant foods, which is ideal for feeding aquarium fish. It contains many useful substances that are valuable in the nutrition of the inhabitants of the aquarium.

They live in fresh water

Habitat

Usually daphnia are found in all stagnant water bodies, from the pond to deep lake. These crustaceans are found even in Antarctica. The main condition for the habitat of daphnia is stagnant freshwater with a minimum amount of soil particles.

When daphnia enter the groundwater, they filter the soil and gradually accumulate algae in their intestines, clogging it. These crustaceans do not like polluted water bodies, so they can be used to judge the purity of a river, lake or pond.

They live for about 22 days

In reservoirs where daphnia live, most of their life takes place in the water column. Some species can live on the bottom, eating there dead parts of plant food, the remains of invertebrates. They can also be found in other places - puddles, pits with water. The crustaceans are very sensitive to lighting, and when it is too bright they go to the depths. Large daphnia lives for 110-150 days. The life cycle of other species is much shorter and can be up to 22 days.

Daphnia nutrition

Water fleas almost always live in natural water bodies. Their main food is yeast and blue-green bacteria. A large concentration of unicellular vegetation is observed most often in "blooming" reservoirs, where there are not a huge number of fish.

Crayfish constantly filter water saturated with unicellular microorganisms. They carry out such movements with the help of pectoral legs. Filtered food enters the food groove in the abdominal cavity and only then - into the esophagus. The upper lips with salivary glands and secretion glue food particles into a lump.

Adult individuals with an average concentration of food in the reservoir are able to filter food at a rate of 1–10 ml/t in 24 hours. Daily intake will depend on the body weight of the crustacean. For example, in an adult magna, it reaches 600% of its weight.

In cold weather, crustaceans can hibernate. However, most species with the presence of food stay near the bottom, eating dead plant food and the remains of invertebrates, which Daphnia also feed on in the warm season. Their stomach is always full of plant foods, so crustaceans are considered the best food for aquarium representatives. They are given in dry form, and also run to the fish in a container. The intestines begin to activate thanks to such a diet, since fish cannot fully move in a small amount of water.

There are a number of nuances of reproduction of these objects

Reproduction of individuals

Daphnia are distinguished by a feature - to breed offspring without fertilization. The females of this species have a brood chamber. It is protected by the edge of the shell and is located on the back. Under favorable conditions, an adult can lay 50 to 100 unfertilized eggs. They develop in the cavity, and only females, and leave it on their own. In females, after this, molting begins.

After a few days, the breeding process begins to repeat itself. Already grown individuals are connected to such a cycle, so everything happens very quickly. One female for the entire period of life is able to give offspring up to 25 times. Because of this, in the summer, you can observe in the reservoirs where daphnia live, the reddish color of the water. It is simply teeming with a huge amount of plankton.

With the onset of autumn, males are connected to the breeding process. After fertilization, the shell on the eggs becomes denser. Future offspring are able to withstand frost, as well as the drying up of water bodies, and spread with dust. When spring comes, the breeding cycle begins to repeat itself again. as the females appear. A new population of individuals at different times of the year may differ in body shape.

Conditions for breeding

Many people breed daphnia at home, which is quite simple. However, this process must be given due attention. The color of the water in the tank plays a big role. It should be greenish or light brown.

Don't forget to add yeast

It is impossible to allow other representatives of water bodies, for example, cyclops, to get into the container for daphnia. At home, the diet of crustaceans should consist of dry lettuce or grapes. Baker's yeast is added to the diet. They are crushed to a powder and then filtered through gauze. To start them at home, you need to take water with 50 crustaceans from a natural reservoir with cooked food and only then run it into a prepared vessel.

At our work, microscopic crustaceans, daphnia, are used for biotesting methods. What is biotesting? This is the determination of the toxicity of water or waste using living organisms - test objects. After all, chemical analysis can only determine a certain set of indicators, usually no more than a couple of dozen, and there are millions of toxic substances. Therefore, there are methods for determining the danger different environments for living beings with the help of small organisms. These can be algae, guppy fish, seeds, etc. Or like here - microscopic crustaceans. Daphnia are organisms a few millimeters in size, with a shell covering the body (carapace) and antennae, with which they move in jumps in the water. It gave scientific name their squad cladocerans(lat. Cladocera) And vernacular name — water fleas, due to the way of movement in the water column. They are quite common in stagnant fresh water bodies: ponds, lakes, swamps, even large puddles. We use a special "breed" - a clean line big daphnia(lat. Daphnia magna). Here in the photo and video are one-day-old individuals. And although they are very small size, less than a couple of millimeters, they hardly fit into the optical field of the microscope through which I examined them.

Large, monthly daphnia can be seen with the naked eye, even some details are visible, antennae, eyes, eggs in a pregnant female. Here I was surprised that, it turns out, the shell of Daphnia is covered with small scales. It can only be seen under a microscope.

big daphnia(lat. Daphnia magna) - a species of crustaceans of the Daphnid family, living in North America, Eurasia and Africa. The body is oval, transparent. Females up to 6 mm long, males up to about 2 mm long. A heat-loving animal that lives in reservoirs rich in nutrients.

Small crustaceans are permanent inhabitants of fresh water bodies, deep lakes, and small puddles. Many of them move along the bottom of the reservoir or the leaves of aquatic plants, and some scurry along the surface, periodically waving their antennae. Small puddles and roadside ditches serve as a good habitat for the water flea. In them, the water temperature is close to atmospheric and enriched with oxygen.

Its long forked antennae are covered with pubescent bristles and act as a parachute that slows down the fall. As soon as Daphnia wave these antennae, it jumps up and returns to its original position. By adjusting the frequency of the flapping of the antennae, daphnia can not only "soar", but also rise to the upper layers of the water or, conversely, go to the depths. Thus, they make vertical movements (migrations) associated with the search for food, changes in water temperature or time of day.

Luxurious mustache is not the only one external feature daphnia. With the exception of the head, the entire body of these "water fleas" is enclosed in a transparent bivalve shell of thin chitin, which Daphnia periodically sheds and replaces with a new one. Daphnia's head is elongated in front into a pointed "beak" or "toe", which makes its owner very pretty. True, she has only one eye, but this is the fate of all cladocerans. But it consists of at least two dozen simple eyes, and this is quite enough to detect an accumulation of bacteria or algae - the usual food of Daphnia.

Most cladocerans feed on various microorganisms in the water: bacteria, ciliates, algae. When daphnia approaches food objects, the abdominal legs of the crustacean hidden under the shell come into play. Making hundreds of strokes per minute, some of them drive water under the sink, while others, covered with bristles, filter out what is suitable for food from the water. Eventually the bacteria or algae form into a small lump that pushes up to the mouth.

The next photo shows the empty shell of a dead daphnia. Or maybe just a discarded shell.

And here I tried to experiment with lighting and shoot daphnia in the dark field technique, and not in the light field, as usual. Here, colors and textures are better manifested, but chromatic aberrations and irregularities of the covering drop of water come out more.

And two more videos with live daphnia under a microscope:

In this video, you can see not only how the daphnia drives water through its filtering system with the help of abdominal legs with bristles, but the rapidly beating heart is clearly visible in the upper part of the frame, closer to the back of the crustacean. And yet, I apologize for the details, in the middle of the video, intestinal motility is visible - there Daphnia crap one's pants.

Everyone is familiar with land-dwelling fleas, especially pet owners. It's hard to believe, but there are also water fleas.

Many believe that, by analogy with land insects, they are also capable of biting and sucking blood from a person.

Cancer under the microscope

Let's take a closer look at what a water flea is: how to detect and treat Daphnia bites, and, most importantly, is it capable of biting at all.

Daphnia (Daphnia) are not insects. They are planktonic crustaceans. These microscopic crustaceans are distributed almost all over the world, they are found even in Antarctica in the waters of relict salt lakes. Species of Daphnia - about 150.

Each has its own range, sometimes occupying several continents. Least of all in the tropics. But in temperate latitudes oh they are very common.

Most often you can find the following types of daphnia:

• magna;
• Rulex;
• Cucullata;
• Galeata;

They differ in size - from 0.6 to 6 mm, the number of eggs laid and life expectancy - from 45 days to 3 months.

Daphnia are characterized by vertical migrations during the day. They rise to the surface at night and descend into deeper layers of water during the day. This is how they protect themselves from predators.

Appearance

The rounded body of Daphnia is a transparent chitinous shell, consisting of two flaps fastened on the back. The rear antennae on the front of the head, also covered with chitin, help it move in the water.

Appearance of Daphnia

When a water flea waves two antennae at once, it makes a sharp jump in the water, for which it got its name. The anterior antennae are the olfactory organ.

This crustacean has only one compound eye. It is mobile, consists of several small eyes, in some species their number reaches 300. On the front of the head there is a beak-shaped outgrowth called the rostrum. The pectoral legs of Daphnia, covered with many bristles, are a kind of filter. Passing water through it, the crustacean catches bacteria or unicellular algae. Legs move at a frequency of up to 500 strokes per minute

The transparent shell does not hide the internal organs, which have a peculiar structure. The kidneys are in the upper part, the brain is next to the esophagus, and the heart is on the back. Daphnia is able to change color depending on the saturation of the reservoir with oxygen.

Internal organs of Daphnia

When there is a lot of it, it is yellowish or gray. With a lack of oxygen, the body turns dark brown.

Daphnia is active only in the warm season. She waits the winter in the bottom layer of water.

Nutrition

Due to certain biological features The main food of Daphnia is the simplest microorganisms:

1. ciliates;
2. fungal spores;
3. bacteria;
4. unicellular algae.

Daphnia can serve as a natural filter for cleaning aquariums. During the day, a water flea is able to eat an amount of food 6 times its own weight.

The nutrition process consists of several stages:

• the front legs, with their rhythmic movement, create a current of water;
• the bristles located on them filter food, sending it into the groove, and then into the esophagus.

In winter, Daphnia's main food is detritus.

Life cycle, reproduction and habitat

Reproduction in these crustaceans depends on the time of year and the availability of sufficient food. In the warm period, the population consists only of parthenogenetic females, whose eggs are capable of producing a new generation without fertilization. The Daphnia embryo develops in a special brood chamber. During this time, he observed several links.

Young females emerge from the brood chamber alive and after 4 days are capable of reproduction.

Brood Daphnia

As the day gets shorter and the temperature in the pond drops, the amount of food decreases. At this time, males can hatch from unfertilized eggs. They are smaller in size, swim faster and have a different structure of motor antennae and pectoral legs.

After fertilization, the so-called resting eggs are formed. They are able to fall into anabiosis and spread by birds, getting into their intestines, where they remain viable.

Daphnia can only exist in still water. The number of soil particles in it should be minimal. If they fall into running water, then along with food they swallow the smallest grains of sand, which gradually clog the intestines and lead to the death of the crustacean.

Daphnia are common inhabitants of all types of stagnant water bodies. They will not be able to exist in a public pool, because there is no appropriate food for them. Water fleas are not found in the sea, such a habitat is detrimental to them.

What is the danger of Daphnia for humans

Many people think that water fleas bite. This opinion is erroneous, since crustaceans simply do not have the corresponding organs. For the bites of the water flea, they take damage to the skin from some other insects.

Nevertheless, the harm from the water flea to humans exists and is considerable. Since Daphnia are often used as fish food, aquarists encounter them all the time.

Daphnia as fish food

It is they who are at risk, since these crustaceans are the strongest allergen.

The reason for this is that pollen that enters water bodies is retained in the organisms of daphnia and accumulates in them. During the drying of fish food, the concentration of pollen increases many times over. It is allergic reactions that people often mistake for bites.

Allergy to Daphnia

Statistics say that about half of humanity is allergic to Daphnia.

Daphnia Allergy Symptoms

In addition to skin manifestations similar to hives, there are other symptoms of an allergy to a water flea:

1. skin itching;
2. allergic rhinitis, which is manifested by nasal congestion and sneezing, sometimes clear mucous discharge from it;
3. allergic conjunctivitis, accompanied by lacrimation;
4. bronchospasm with difficulty breathing.

An extreme manifestation of an allergy can be bronchial asthma.

Treatment

At the first sign of an allergy, you should visit a doctor. After setting skin tests, it will be possible to judge its cause.

If Daphnia is to blame, you will have to stop using them to feed the fish.

Examples of antihistamines

The doctor will select the necessary antihistamines for treatment.

Conclusion

Water fleas can be dangerous to humans due to their allergenicity. If there is a swimming pool on the site, they may well get a divorce there. In this case, the question arises: how to get rid of water fleas in the pool?

From the crustaceans themselves, chlorination of water helps well. Sleeping Daphnia eggs can remain viable even in such conditions, but individuals that emerge from them will die. So that the problem does not arise again and again, the water must be changed more often and be sure to disinfect.

Video: Breeding and selling daphnia as a business idea

photo can be enlarged

Daphnia are predominantly small crustaceans belonging to the Daphniidae family. This family, in turn, is included in Cladocera, which also includes gammaruses, brine shrimp, and others. For peculiar sharp movements, it is often called the "water flea". Not to mention the features of movement, daphnia appearance also looks like a flea. However, the latter refers to insects and has a very distant common ancestor with crustaceans, since both classes are included in the phylum Arthropoda. All types of daphnia have different variations, and sometimes representatives of the same species are very different from each other. Features of the phenotype, size and shape of the body depend on the area of ​​​​origin and specific environmental conditions. Representatives of the genus Moina have a significant similarity with Daphnia.

It is important to distinguish Daphnia from other "water fleas" such as copepods, species of cyclops and barnacles, which often live in the same places. Sharp movements, body shape and, to a lesser extent, coloration, are the best criteria to distinguish without having to look under a microscope.

The genus Daphnia has a very wide distribution, including Antarctica, where Daphnia studeri, previously attributed to the genus Daphniopsis, was found in the relict salt lakes of the Vestfold oasis. At the beginning of the 20th century, the opinion about the cosmopolitan distribution of most species prevailed, but later it turned out that the faunas of different continents differ greatly. Some species, however, have very wide ranges and are distributed on several continents. Smallest number species is typical for equatorial regions, where daphnia are rare. The fauna of subtropics and temperate latitudes is the most diverse. In recent decades, the ranges of many species have changed due to their dispersal by humans. Thus, a species from the New World, D. ambigua, was introduced into Europe. In many reservoirs in the southern United States, D. lumholtzi has become common, which until then was found only in the Old World.

photo can be enlarged

In ponds and puddles of central Russia, they are often found, and therefore the most popular among, are the following crustaceans of the genus Daphnia. Daphnia magna (D. magna), female - up to 6 mm, male - up to 2 mm, newborns - 0.7 mm. Ripen within 10-14 days. Litters in 12-14 days. In laying up to 80 eggs, but usually 20-30. The life expectancy of this crustacean is up to 3 months. Daphnia puleks (D. pulex), female - up to 3-4 mm, male - 1-2 mm. Litters in 3-5 days. In laying up to 25 eggs, but usually 10-12. Pulex live 26-47 days. In the lakes of the temperate zone of Eurasia, D. cucullata, D. galeata, D. cristata and several other species are often found.

Daphnia are small crustaceans, the body size of adults is from 0.6 to 6 mm. They inhabit all types of stagnant continental water bodies, and are also found in many slow-flowing rivers. In puddles, ponds and lakes, they often have a high abundance and biomass. Daphnia are typical planktonic crustaceans, spending most of their time in the water column. Different kinds inhabit small temporary reservoirs, littoral and pelagial lakes. Quite a few species, especially those inhabiting arid regions, are halophiles living in brackish, saline and hypersaline continental water bodies. Such species include, for example, D. magna, D. atkinsoni, D. mediterranea, as well as most of the species previously assigned to the genus Daphniopsis.

Most of the time they spend in the water column, moving in sharp leaps due to the flapping of the second antennae, which are covered with special feathered bristles. Many daphnia are also able to slowly crawl along the bottom or walls of blood vessels due to water currents created by the pectoral legs; the antennae are motionless during this method of movement.

Perhaps the elusiveness of rapidly jumping crustaceans reminded scientists of the legend of the nymph Daphne, almost overtaken by Apollo, but never caught by him? Or maybe the mustache of the crustaceans seemed to someone like the branches of an evergreen laurel, into which a beautiful nymph has turned.

Ovid in the poem "Metamorphoses" told how one day the golden-haired god of light Apollo inadvertently laughed at the son of Aphrodite Eros (or, as the Greeks also called him, Eros). The offended god of love from a golden bow struck the silver-faced patron of the muses in the very heart. Having once met the beautiful Daphne, daughter of the river god Peneus, Apollo fell in love with her at first sight, but the beautiful nymph, whom Eros struck with an arrow that kills love, started to run away from him with the speed of the wind. Then Apollo chased after her, but the nymph only ran faster and faster from the beautiful god. When her strength began to dry up, Daphne began to beg her father to deprive her of her appearance, which brought her only grief. Old Peney took pity on his daughter. And at that moment, when it seemed that Apollo had already caught up with the beauty, she turned into a laurel tree.

The saddened Apollo did not want to part with his beloved. He decorated his quiver and cithara with laurel leaves, and placed a wreath of laurel branches on his head, the aroma of which always reminded him of the elusive Daphne.

Reproduction in nature

photo can be enlarged

IN summer months daphnia are often found in flowering ponds and lakes that have a high concentration of algae. The fertility of Daphnia is simply amazing, which is associated with the implementation of parthenogenesis.

Parthenogenesis is the ability of self-reproduction without the need for fertilization, when the offspring completely repeats the parent's genotype, and any differences in the physiological state are determined by environmental conditions. Parthenogenesis allows daphnia to reproduce rapidly in favorable conditions, shortly after hatching from eggs. In nature, in late spring, summer and early autumn, depending on temperature, food availability and the presence of their metabolic products, daphnia reproduces parthenogenetically, giving rise to an average of 10 nauplii per adult. During this period, only females are present in the reservoir. The developing embryo is often visible inside the mother's body without a microscope. Females of the next generation are capable of parthenogenesis after 4 days of development, while childbirth occurs every three days. For your life cycle a female may give birth 25 times, but in practice this number is slightly less and the female tends to produce no more than 100 offspring.

With a lack of food, some eggs develop into males, and females begin to produce eggs that must be fertilized. The latter develop into small embryos which then hibernate, covered with a dark brown/black saddle shell known as the ephippium. In this form, daphnia can tolerate harsh environmental conditions, short-term drying of the reservoir and even its freezing. Females born to form ephippium are easily distinguished from parthenogenetic individuals because the developing ephippium is present as a black spot at the posterior end of the body. When environmental conditions become favorable again, a generation appears from the eggs, which, in turn, gives birth only to females, while all males die before the onset of unfavorable conditions.

Fishing in natural waters

photo can be enlarged

They catch daphnia with a net. A net for this needs a special one - with a long handle up to 2-3 meters, usually made up of several screwed segments, about 25-30 cm in diameter and a fabric cone about 50-60 cm long with a rounded end. The net ring is made of durable material, such as stainless steel wire with a diameter of 3-5mm. If you make it thinner, it will easily bend, and taking into account possible snags at the bottom ... But the most difficult thing is to choose a fabric for the net. Here, synthetic materials are preferable, such as nylon, which do not rot from prolonged contact with water. The size of the net mesh depends on what you are going to catch, a very small fabric greatly slows down the net in the water, so it is better to have several interchangeable rings with different fabrics for catching food of different sizes.

Nets act calmly, smoothly, without special efforts driving it with a "eight" in places of accumulation of daphnia. We spent a couple of times, took it out, shook out the catch, and began to fish further. If you push a full net, then many daphnia crumple and die, so it is better to take it out more often with small portions of prey. And then greed, you know, does not lead to good. For fishing, it is better to prefer smaller reservoirs, for example, the same puddles - there daphnia are more accustomed to oxygen starvation and will more easily endure further transportation. True, it is difficult to catch with a typical net in small puddles, there you have to use a net with a shorter cone - otherwise it starts to cling to the bottom and understand the turbidity. In order not to catch hydra with daphnia, one should try to catch prey away from thickets of aquatic plants or objects in the water to which it can be attached. And in no case is it recommended to catch food in reservoirs where fish live - with such food it is easy to introduce pathogens of various diseases.

Captured daphnia are placed in a container - a can or a special cann for transportation. It is advisable to strain the catch through a sparse mesh before pouring to remove any debris and any large unwanted guests - swimming beetles or large dragonfly larvae. It is highly desirable to have a battery-powered compressor in the transport tank - it will allow you to keep most of the catch alive during the journey home.

Houses of captured daphnia are poured into a wide flat vessel, such as a white enameled basin. There, for some time, all unwanted organisms settle on the bottom and walls, on a white background it is easy to detect dragonfly and leech larvae, and everything else that has nothing to do with daphnia. In the same place, dead crustaceans accumulate at the bottom. When feeding, daphnia are caught with a net, the water in which they are located cannot be poured into the aquarium! These crustaceans are best suited for feeding small aquarium fish, such as or. For larger fish it is more convenient to use live or frozen.

In nature, daphnia live in ponds and large puddles, where they feed on various bacteria and phytoplankton. However, such water bodies are often polluted with industrial waste or fish are found in them. Both can lead to diseases in aquarium inhabitants.

Daphnia can also be dangerous for the aquarists themselves. In spring and early summer, the diet of crustaceans often includes pollen from flowering plants, carried by the wind into water bodies. Daphnia caught at this time and dried for future use when feeding fish can cause a painful reaction in people suffering from pollen allergies. This fact, in particular, can explain the often encountered opinion that the aquarium is harmful to health. In fact, the reason is pollen, which during the period of mass flowering of grasses is literally “stuffed” with crustaceans.

Breeding at home

photo can be enlarged

For growing daphnia, a 15 liter plastic container, or any other, is perfect. In this case, several recommendations can be noted. Avoid container material that is water soluble or releases harmful chemicals. If a metal container is used, it must be made of stainless steel. Aluminum oxides form a film, but some aluminum is still released. As in the case of a conventional aquarium, a large area of ​​​​contact with air is necessary for gas exchange, because daphnia are very demanding on the oxygen content. If the container is located outdoors, in strong sunlight or other lighting, it is recommended to use more than 40 liter volumes so that the water environment is stable. In addition, when black pond material is used, it heats up more than transparent or yellow, which should also be taken into account.

For those who wish to have a small number of daphnia per week, the culture can be maintained in a two liter bottle. For growing in an aquarium, it is a good idea to connect the lighting through a timer, which can be purchased at an electrical appliance store. Daphnia magna has been found to prefer low aeration. In theory, aeration not only supports gas exchange, but also stabilizes water conditions and prevents crop inhibition. Daphnia pulex also likes low aeration. It is necessary to avoid small air bubbles that can get under the daphnia carapace, raise them to the surface, interfere with feeding and eventually lead to death.

The best nutrient medium for the culture are blue-green algae. Usually, these are free-floating green algae that tend to turn water into " pea soup”, yeast (Sacromyces spp and related fungi) and bacteria. The combination of the above objects makes the culture maintenance process successful, yeast and algae complement each other.

frozen daphnia
photo can be enlarged

Microalgae are consumed by daphnia in huge quantities, and an abundance of crustaceans is observed in places where water bodies bloom. There are a number of ways to ensure the development of algae that require minimal effort.

Placing the culture container in direct sunlight guarantees algae development within two weeks, usually earlier. Their spores are airborne and colonize water bodies, but, as a rule, some algae is added to the water to speed up flowering. Use of plant fertilizers, such as Miracle grow. Once a week, 1 teaspoon of fertilizer is added to a 4 liter container. The container must be placed in direct sunlight. Aeration and slow movement of water is necessary. A system must be built whereby the first algae tank already has green color, the second will acquire this shade within two days, the third within two more days, etc.. When the first container becomes light green (after 2 weeks), it is poured into the Daphnia culture. The empty container is refilled with the mixture with the addition of a small amount of water from the second container. Thus, every two days the aquarist has 4 liters of blooming water ready to be fed to the daphnia.

The advantages of algae are the ease of preparation and the extremely rapid development of the culture of daphnia that consume them. There are no disadvantages, except for the need to constantly restart the tanks. Daphnia should not be placed in an environment that is too rich in algae, because algae tend to raise the pH up to 9. High alkalinity is associated with an increase in ammonia toxicity, even at low concentrations.

Bakers', brewers', and virtually all other types of yeast are suitable for daphnia cultivation, but it is recommended that no more than 28 g per 20 liters of water be used daily. In the case of using yeast, algae can be added to the water, which will prevent environmental pollution. It is important not to overdo it with the addition of yeast, excess will pollute the environment and destroy the daphnia culture.

dried daphnia
photo can be enlarged

Some baker's yeast comes mixed with active ingredients such as calcium sulfate, ascorbic acid which stimulate the development of fungi. These components themselves are harmless to the culture, however, ascorbic acid can lower the pH of the medium to 6, which is far from ideal for Daphnia. This usually happens with overfeeding.

The advantage of yeast as a nutrient medium is that it is easy to obtain and requires minimal effort to prepare and maintain the culture. However, they are not as valuable in terms of nutrition for daphnia as algae. Crustaceans need to consume more yeast than algae to obtain the same nutritional value.

Daphnia lives in a wide range of temperatures. The optimum temperature is 18-22 0C. D. pulex thrives at temperatures above 10 0C. Moina withstands even more severe fluctuations, 5-31 0C; the optimum is 24-31 0C. Moina's increased resistance to temperature makes it the preferred cultivar when D. magna is natural conditions the optimum is reached only once a year.

Daphnia are tolerant of dirty water, and dissolved oxygen levels can range from near zero to supersaturated. Like brine shrimp, the ability of daphnia to survive in an oxygen-poor environment is due to the ability to form hemoglobin. Hemoglobin production can be accelerated by increasing temperature and population density. As well as in the case of Artemia, Daphnia does not tolerate active aeration with small air bubbles that can kill it.

Daphnia production is a relatively easy process. However, there are measures to increase the productivity of cultivation. Good aeration, good to the extent that the water is oxygenated, but not overly aerated, is a major factor in increasing productivity. Some species prefer no aeration, but Daphnia magna is best bred in its presence. In addition, this allows you to increase the density of the culture, the circulation of water reduces algal plaque on the walls of the vessel, and also transfers food particles to a suspended state, which is typical for the natural diet of daphnia. The only drawback is that small air bubbles fill the carapace of crustaceans, which float up and cannot feed. Air atomizer should be avoided altogether, or it should be very coarse to create large bubbles. Convenient in terms of aeration is the "bio-foam" filter. It is usually used in a fry tank but is ideal for Daphnia. It captures large particles and promotes their decomposition to feed the algae.

Regular selection/collection of culture. This event maintains a constant increase in culture and provides daphnia with the opportunity to accumulate oxygen and food faster. 24-hour daylight hours increase the productivity of daphnia, but this is an optional measure. Also, do not keep Daphnia in the dark for 24 hours, because this stimulates the crustaceans to form ephippia. The mode and degree of water replacement depends on the nutrient medium used, but, in any case, they are necessary for purification from metabolites and toxins.

When it comes to cultivating Daphnia, harvesting it can be a real challenge, but it is an integral part of the whole breeding process. Otherwise, overpopulation becomes a serious problem. Even if you have to shake out the crustaceans in the sink, this must be done, because the culture can become unstable. If the aquarist cultivates daphnia at temperatures below 25 0C, it makes sense to start catching in the middle of the second week. This is because most crops take several days to adapt and start reproducing. When culling / trapping, a net is used that has meshes large enough to pass young crustaceans, but small enough to catch adults. Some aquarists recommend pouring ¼ of the container through the net and then refilling the volume with fresh water and culture medium. No more than ¼ of the population can be caught daily, which also depends on the quality of cultivation. Catching can be done during the day when aeration stops, when all daphnia rise to the upper layer of water.

Caught crustaceans can live for several days in a jig with fresh water. They exhibit normal activity at elevated temperatures. However the nutritional value daphnia is gradually decreasing because they are starving and for best effect you need to provide them with food. For a long time, crustaceans can be stored frozen if they are frozen in water with a low salt content (0.007 ‰, density - 1.0046). Of course, this will kill the daphnia, by washing out the nutrients, their value will decrease, almost all enzymatic activity will be lost within 10 minutes, and after an hour ½ of the free amino acids and all related ones will be lost. Fish are not so willing to eat frozen crustaceans.